numpy - How do I write many nested for-loops in a few lines of Python code? -


what have: have list list123=[-13,3,12,1] , 2-by-4-matrix matrix123=numpy.zeros((2,4), dtype=decimal).

what want: want change entries of matrix entry of list , print terminal. there 4^(2*4)=65536 possible combinations. want print every combination.

how now: here current code:

list123=[-13,3,12,1]  matrix123=numpy.zeros((2,4), dtype=decimal)  k=0 k in list123:     matrix123[0,0]=k     k in list123:         matrix123[0,1]=k         k in list123:             matrix123[0,2]=k             k in list123:                 matrix123[0,3]=k                 k in list123:                     matrix123[1,0]=k                     k in list123:                         matrix123[1,1]=k                         k in list123:                             matrix123[1,2]=k                             k in list123:                                 matrix123[1,3]=k                                 print matrix123                                 print " "

my question: what more compact way write in few lines of code? need same 23-by-27 matrix. mean have write code 23*27=621 for-loops manually, if don't find more compact way.

you can use itertools.product:

import itertools  list123 = [-13, 3, 12, 1]  matrix in itertools.product(list123, repeat=8):   print matrix

it output possible solution of length 8 -13, 3, 12 , 1. matrix tuple 8 numbers, being possible solutions.

if need output result in real numpy.matrix form, can create them on fly (even though take more time).

import numpy np  prod in itertools.product(list123, repeat=8):   print np.matrix([prod[:4], prod[4:]])

or using reshape improve readability (thanks @menglongli)

for prod in itertools.product(list123, repeat=8):   print np.reshape(prod, (2, 4))

it gave 65536 results expected.


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